Milankovitch cycles 1

Milankovitch cycles

Past and future Milankovitch cycles. VSOP allows prediction of past and future orbitalparameters with great accuracy. ε is obliquity (axial tilt). e is eccentricity. ϖ is longitude

of perihelion. esin(ϖ) is the precession index, which together with obliquity, controls theseasonal cycle of insolation. is the calculated daily-averaged insolation at the top

of the atmosphere, on the day of the summer solstice at 65 N latitude. Benthic forams andVostok ice core show two distinct proxies for past global sealevel and temperature, fromocean sediment and Antarctic ice respectively. Vertical gray line is current conditions, at

2 ky A.D.

Milankovitch theory describes thecollective effects of changes in theEarth's movements upon its climate,named after Serbian geophysicist andastronomer Milutin Milanković, whoworked on it during First World Warinternment. Milankovićmathematically theorized thatvariations in eccentricity, axial tilt, andprecession of the Earth's orbitdetermined climatic patterns on Earththrough orbital forcing.

The Earth's axis completes one fullcycle of precession approximatelyevery 26,000 years. At the same timethe elliptical orbit rotates more slowly.The combined effect of the twoprecessions leads to a 21,000-yearperiod between the astronomicalseasons and the orbit. In addition, theangle between Earth's rotational axisand the normal to the plane of its orbit(obliquity) oscillates between 22.1 and24.5 degrees on a 41,000-year cycle. Itis currently 23.44 degrees anddecreasing.

Similar astronomical theories had beenadvanced in the 19th century by JosephAdhemar, James Croll and others, but verification was difficult due to the absence of reliably dated evidence anddoubts as to exactly which periods were important. Not until the advent of deep-ocean cores and a seminal paper byHays, Imbrie, and Shackleton, "Variations in the Earth's Orbit: Pacemaker of the Ice Ages", in Science (1976)[1] didthe theory attain its present state.

Earth’s movements

As the Earth spins around its axis and orbits around the Sun, several quasi-periodic variations occur due togravitational interactions. Although the curves have a large number of sinusoidal components, a few components aredominant.[2] Milankovitch studied changes in the orbital eccentricity, obliquity, and precession of Earth'smovements. Such changes in movement and orientation alter the amount and location of solar radiation reaching theEarth. This is known as solar forcing (an example of radiative forcing). Changes near the north polar area, about 65degrees North, are considered important due to the great amount of land. Land masses respond to temperaturechange more quickly than oceans, which have a higher effective heat capacity, because of the mixing of surface anddeep water and the fact that the specific heat of solids is generally lower than that of water.

Milankovitch cycles 2

Orbital shape (eccentricity)

Circular orbit, no eccentricity. Orbit with 0.5 eccentricity.

The Earth's orbit is an ellipse. The eccentricity is a measure of the departure of this ellipse from circularity. Theshape of the Earth's orbit varies in time between nearly circular (low eccentricity of 0.005) and mildly elliptical (higheccentricity of 0.058) with the mean eccentricity of 0.028. The major component of these variations occurs on aperiod of 413,000 years (eccentricity variation of ±0.012). A number of other terms vary between components95,000 and 125,000 years (with a beat period 400,000 years), and loosely combine into a 100,000-year cycle(variation of −0.03 to +0.02). The present eccentricity is 0.017.If the Earth were the only planet orbiting our Sun, the eccentricity of its orbit would not perceptibly vary even over aperiod of a million years. The Earth's eccentricity varies primarily due to interactions with the gravitational fields ofJupiter and Saturn. As the eccentricity of the orbit evolves, the semi-major axis of the orbital ellipse remainsunchanged. From the perspective of the perturbation theory used in celestial mechanics to compute the evolution ofthe orbit, the semi-major axis is an adiabatic invariant. According to Kepler's third law the period of the orbit isdetermined by the semi-major axis. It follows that the Earth's orbital period, the length of a sidereal year, alsoremains unchanged as the orbit evolves. As the semi-minor axis is decreased with the eccentricity increase, theseasonal changes increase.[3] But the mean solar irradiation for the planet changes only slightly for smalleccentricity, due to Kepler's second law.The same average irradiation does not correspond to the average of corresponding temperatures (due to non-linearityof the Stefan–Boltzmann law). For an irradiation with corresponding temperature 20 °C and its symmetric variation±50% (e.g. from the seasons change[4]) we obtain asymmetric variation of corresponding temperatures with theiraverage 16 °C (i.e. deviation −4 °C). And for the irradiation variation during a day (with its average correspondingalso to 20 °C) we obtain the average temperature (for zero thermal capacity) −113 °C.The relative increase in solar irradiation at closest approach to the Sun (perihelion) compared to the irradiation at thefurthest distance (aphelion) is slightly larger than four times the eccentricity. For the current orbital eccentricity thisamounts to a variation in incoming solar radiation of about 6.8%, while the current difference between perihelionand aphelion is only 3.4% (5.1 million km). Perihelion presently occurs around January 3, while aphelion is aroundJuly 4. When the orbit is at its most elliptical, the amount of solar radiation at perihelion will be about 23% morethan at aphelion.

Milankovitch cycles 3

Season durations[5]

Year Northern Hemisphere Southern Hemisphere Date: GMT Season duration

2005 Winter solstice Summer solstice 21 December 2005 18:35 88.99 days

2006 Spring equinox Autumn equinox 20 March 2006 18:26 92.75 days

2006 Summer solstice Winter solstice 21 June 2006 12:26 93.65 days

2006 Autumn equinox Spring equinox 23 September 2006 4:03 89.85 days

2006 Winter solstice Summer solstice 22 December 2006 0:22 88.99 days

2007 Spring equinox Autumn equinox 21 March 2007 0:07 92.75 days

2007 Summer solstice Winter solstice 21 June 2007 18:06 93.66 days

2007 Autumn equinox Spring equinox 23 September 2007 9:51 89.85 days

2007 Winter solstice Summer solstice 22 December 2007 06:08

Orbital mechanics requires that the length of the seasons be proportional to the areas of the seasonal quadrants, sowhen the eccentricity is extreme, the Earth's orbital motion becomes more nonuniform and the lengths of the seasonschange. When autumn and winter occur at closest approach, as is the case currently in the northern hemisphere, theearth is moving at its maximum velocity and therefore autumn and winter are slightly shorter than spring andsummer. Thus, summer in the northern hemisphere is 4.66 days longer than winter and spring is 2.9 days longer thanautumn. But as the orientation of Earth's orbit changes relative to the Vernal Equinox due to apsidal precession theway the length of the seasons are altered by the nonuniform motion changes since different sections of the orbit areinvolved. When the Earth's apsides are aligned with the equinoxes the length of Spring and Summer (together)equals that of Autumn and Winter. When they are aligned with the solstices either Spring and Summer or Autumnand Winter will be at its longest. Increasing the eccentricity lengthens the time spent near aphelion and shortens thetime near perihelion.Changes to the eccentricity do not by themselves change the length of the anomalistic year or the Earth's meanmotion along its orbit since they are both functions of the semi-major axis.

Axial tilt (obliquity)

22.1–24.5° range of Earth's obliquity.

The angle of the Earth's axial tilt (obliquity of the ecliptic) varies withrespect to the plane of the Earth's orbit. These slow 2.4° obliquityvariations are roughly periodic, taking approximately 41,000 years toshift between a tilt of 22.1° and 24.5° and back again. When theobliquity increases, the amplitude of the seasonal cycle in insolationincreases, with summers in both hemispheres receiving more radiativeflux from the Sun, and winters less. Conversely, when the obliquitydecreases, summers receive less insolation and winters more.

But these changes of opposite sign in summer and winter are not of thesame magnitude everywhere on the Earth's surface. At high latitude theannual mean insolation increases with increasing obliquity, whilelower latitudes experience a reduction in insolation. Cooler summersare suspected of encouraging the onset of an ice age by melting less of

the previous winter's precipitation. Because most of the planet's snow and ice lies at high latitude, it can be arguedthat lower obliquity favors ice ages for two reasons: the reduction in overall summer insolation and the additionalreduction in mean insolation at high latitude.

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Scientists using computer models to study more extreme tilts than those that actually occur have concluded thatclimate extremes at high obliquity would be particularly threatening to advanced forms of life that presently exist onEarth. They noted that high obliquity would not likely sterilize a planet completely, but would make it harder forfragile, warm-blooded land-based life to thrive as it does today.[6]

Currently the Earth is tilted at 23.44 degrees from its orbital plane, roughly halfway between its extreme values. Thetilt is in the decreasing phase of its cycle, and will reach its minimum value around the year 11,800 CE ; the lastmaximum was reached in 8,700 BCE. This trend, by itself, tends to make winters warmer and summers colder withan overall cooling trend leading to an ice age, but the 20th century instrumental temperature record shows a suddenrise in global temperatures and a concurring glacial melt has led the scientific community to attribute recent changesto greenhouse gas emissions.[7]

Axial precession

Precessional movement.

Precession is the trend in the direction of the Earth's axis of rotationrelative to the fixed stars, with a period of roughly 26,000 years. Thisgyroscopic motion is due to the tidal forces exerted by the Sun and theMoon on the solid Earth, which has the shape of an oblate spheroidrather than a sphere. The Sun and Moon contribute roughly equally tothis effect.

When the axis points toward the Sun in perihelion, one polarhemisphere has a greater difference between the seasons while theother has milder seasons. The hemisphere that is in summer atperihelion receives much of the corresponding increase in solarradiation, but that same hemisphere in winter at aphelion has a colderwinter. The other hemisphere will have a relatively warmer winter andcooler summer.When the Earth's axis is aligned such that aphelion and perihelion

occur near the equinoxes, the Northern and Southern Hemispheres will have similar contrasts in the seasons.At present, perihelion occurs during the southern hemisphere's summer, and aphelion is reached during the southernwinter. Thus the southern hemisphere seasons are somewhat more extreme than the northern hemisphere seasons,when other factors are equal.

Milankovitch cycles 5

Apsidal precession

Planets orbiting the Sun follow elliptical (oval) orbits that rotate gradually over time(apsidal precession). The eccentricity of this ellipse is exaggerated for visualization. Mostorbits in the Solar System have a much smaller eccentricity, making them nearly circular.

Effects of precession on the seasons (using the Northern Hemisphere terms).

In addition, the orbital ellipse itselfprecesses in space, primarily as a resultof interactions with Jupiter and Saturn.Smaller contributions are also made bythe sun's oblateness and by the effectsof General Relativity that are wellknown for Mercury. The total orbitalprecession is in the same sense to thegyroscopic motion of the axis ofrotation, shortening the period of theprecession of the equinoxes withrespect to the perihelion from 25,771.5to ~21,636 years. Apsidal precessionoccurs in the plane of the Ecliptic andalters the orientation of the Earth'sorbit relative to the Ecliptic. Incombination with changes to theeccentricity it alters the length of theseasons.

Orbital inclination

The inclination of Earth's orbit driftsup and down relative to its presentorbit. Milankovitch did not study thisthree-dimensional movement. Thismovement is known as "precession ofthe ecliptic" or "planetary precession".

More recent researchers noted this driftand that the orbit also moves relative tothe orbits of the other planets. Theinvariable plane, the plane thatrepresents the angular momentum ofthe Solar System, is approximately theorbital plane of Jupiter. The inclinationof Earth's orbit drifts up and downrelative to its present orbit with a cyclehaving a period of about 70,000 years.

The inclination of the Earth's orbit has a 100,000-year cycle relative to the invariable plane. This is very similar tothe 100,000-year eccentricity period. This 100,000-year cycle closely matches the 100,000-year pattern of ice ages.

It has been proposed that a disk of dust and other debris exists in the invariable plane, and this affects the Earth'sclimate through several possible means. The Earth presently moves through this plane around January 9 and July 9,when there is an increase in radar-detected meteors and meteor-related noctilucent clouds.[8][9]

A study of the chronology of Antarctic ice cores using oxygen-nitrogen ratios in air bubbles trapped in the ice, which appear to respond directly to the local insolation, concluded that the climatic response documented in the ice cores

Milankovitch cycles 6

was driven by northern hemisphere insolation as proposed by the Milankovitch hypothesis (Kawamura et al., Nature,23 August 2007, vol 448, pp 912–917). This is an additional validation of the Milankovitch hypothesis by arelatively novel method, and is inconsistent with the "inclination" theory of the 100,000-year cycle.

ProblemsBecause the observed periodicities of climate fit so well with the orbital periods, the orbital theory has overwhelmingsupport. Nonetheless, there are several difficulties in reconciling theory with observations.

The nature of sediments can vary in a cyclicfashion, and these cycles can be displayed in thesedimentary record. Here, cycles can be observed

in the colouration and resistance of differentstrata.

100,000-year problem

The 100,000-year problem is that the eccentricity variations have asignificantly smaller impact on solar forcing than precession orobliquity and hence might be expected to produce the weakest effects.The greatest observed response is at the 100,000-year timescale, whilethe theoretical forcing is smaller at this scale, in regard to the iceages.[10] However, observations show that during the last 1 millionyears, the strongest climate signal is the 100,000-year cycle. Inaddition, despite the relatively great 100,000-year cycle, some haveargued that the length of the climate record is insufficient to establish astatistically significant relationship between climate and eccentricityvariations.[11] Various explanations for this discrepancy have beenproposed, including frequency modulation[12] or various feedbacks(from carbon dioxide, cosmic rays, or from ice sheet dynamics). Some models can reproduce the 100,000-yearcycles as a result of non-linear interactions between small changes in the Earth's orbit and internal oscillations of theclimate system.[13][14]

400,000-year problemThe 400,000-year problem is that the eccentricity variations have a strong 400,000-year cycle. That cycle is onlyclearly present in climate records older than the last million years. If the 100ka variations are having such a strongeffect, the 400ka variations might also be expected to be apparent. This is also known as the stage 11 problem, afterthe interglacial in marine isotopic stage 11 that would be unexpected, if the 400,000-year cycle has an impact onclimate. The relative absence of this periodicity in the marine isotopic record may be due, at least in part, to theresponse times of the climate system components involved—in particular, the carbon cycle.

Milankovitch cycles 7

Stage 5 problemThe stage 5 problem refers to the timing of the penultimate interglacial (in marine isotopic stage 5) that appears tohave begun ten thousand years in advance of the solar forcing hypothesized to have caused it (the causalityproblem).

Effect exceeds cause

420,000 years of ice core data from Vostok, Antarctica researchstation.

The effects of these variations are primarily believed tobe due to variations in the intensity of solar radiationupon various parts of the globe. Observations showclimate behavior is much more intense than thecalculated variations. Various internal characteristics ofclimate systems are believed to be sensitive to theinsolation changes, causing amplification (positivefeedback) and damping responses (negative feedback).

The unsplit peak problem

The unsplit peak problem refers to the fact thateccentricity has cleanly resolved variations at both the95 and 125ka periods. A sufficiently long, well-datedrecord of climate change should be able to resolve both frequencies,[15] but some researchers interpret climaterecords of the last million years as showing only a single spectral peak at 100ka periodicity. It is debatable whetherthe quality of existing data ought to be sufficient to resolve both frequencies over the last million years.

The transition problem

Variations of Cycle Times, curves determined from ocean sediments

The transition problem refers to theswitch in the frequency of climatevariations 1 million years ago. From1–3 million years, climate had adominant mode matching the 41kacycle in obliquity. After 1 millionyears ago, this switched to a 100kavariation matching eccentricity, forwhich no reason has been established.

Milankovitch cycles 8

Identifying dominant factorMilankovitch believed that decreased summer insolation in northern high latitudes was the dominant factor leadingto glaciation, which led him to (incorrectly) deduce an approximate 41ka period for ice ages.[16] Subsequent researchhas shown that the 100ka eccentricity cycle is more important, resulting in 100,000-year ice age cycles of theQuaternary glaciation over the last million years.

Present and future conditions

Past and future of daily average insolation at top of the atmosphere on the day of thesummer solstice, at 65 N latitude. The green curve is with eccentricity e hypothetically setto 0. The red curve uses the actual (predicted) value of e. Blue dot is current conditions, at

2 ky A.D.

As mentioned above, at present,perihelion occurs during the southernhemisphere's summer and aphelionduring the southern winter. Thus thesouthern hemisphere seasons shouldtend to be somewhat more extremethan the northern hemisphere seasons.The relatively low eccentricity of thepresent orbit results in a 6.8%difference in the amount of solarradiation during summer in the two hemispheres.Since orbital variations are predictable,[17] if one has a model that relates orbital variations to climate, it is possible torun such a model forward to "predict" future climate. Two caveats are necessary: that anthropogenic effects maymodify or even overwhelm orbital effects; and that the mechanism by which orbital forcing influences climate is notwell understood.

The amount of solar radiation (insolation) in the Northern Hemisphere at 65° N seems to be related to occurrence ofan ice age. Astronomical calculations show that 65° N summer insolation should increase gradually over the next25,000 years.[18] A regime of eccentricity lower than the current value will last for about the next 100,000 years.Changes in northern hemisphere summer insolation will be dominated by changes in obliquity ε. No declines in 65°N summer insolation, sufficient to cause a glacial period, are expected in the next 50,000 years.An often-cited 1980 study by Imbrie and Imbrie determined that, "Ignoring anthropogenic and other possible sourcesof variation acting at frequencies higher than one cycle per 19,000 years, this model predicts that the long-termcooling trend that began some 6,000 years ago will continue for the next 23,000 years."[19]

More recent work by Berger and Loutre suggests that the current warm climate may last another 50,000 years.[20]

Other planets in the Solar SystemOther planets in the Solar System have been discovered to have Milankovitch cycles. Mostly these cycles are not asintense or complex as the Earth's cycles, but do have a global geological impact with respect to the movement ofmobile solids like Water or Nitrogen ices or hydrocarbon lakes.• Mars's polar caps vary in extent due to orbital instability related to a latent Milankovitch cycle. [21][22][23]• Saturn's moon Titan has a ~60,000-year cycle that changes the location of the methane lakes.[24] [25]• Neptune's moon Triton has a similar variation to Titan with respect to migration of solid nitrogen deposits over

long time scales.[26][27][28]

Milankovitch cycles 9

References[1] Hays, J. D.; Imbrie, J.; Shackleton, N. J. (1976). "Variations in the Earth's Orbit: Pacemaker of the Ice Ages". Science 194 (4270):

1121–1132. doi:10.1126/science.194.4270.1121. PMID 17790893.[2] Girkin, Amy Negich (2005) (PDF). A Computational Study on the Evolution of the Dynamics of the Obliquity of the Earth (http:/ / etd.

ohiolink. edu/ send-pdf. cgi/ Girkin, Amy Negich. pdf?miami1133292203) (Master of Science thesis). Miami University. .[3] Berger A., Loutre M.F., Mélice J.L. (2006). "Equatorial insolation: from precession harmonics to eccentricity frequencies" (http:/ / www.

clim-past-discuss. net/ 2/ 519/ 2006/ cpd-2-519-2006. pdf) (PDF). Clim. Past Discuss. 2 (4): 519–533. doi:10.5194/cpd-2-519-2006. .[4] "Deliverables of IEA SHC – Task 26: Solar Combisystems" (PDF).[5] Data from United States Naval Observatory (http:/ / aa. usno. navy. mil/ data/ docs/ EarthSeasons. php)[6] Williams, D.M., Pollard, P. (2002). "Earth-like worlds on eccentric orbits: excursions beyond the habitable zone" (http:/ / physics. bd. psu.

edu/ faculty/ williams/ 3DEarthClimate/ ija2003. pdf). Inter. J. Astrobio. 1: 21–9. .[7] Kaufman, D.; Schneider, D.; McKay, N.; Ammann, C.; Bradley, R.; Briffa, K.; Miller, G.; Otto-Bliesner, B. et al. (2009). "Recent warming

reverses long-term arctic cooling". Science 325 (5945): 1236–1239. Bibcode 2009Sci...325.1236K. doi:10.1126/science.1173983.PMID 19729653."Arctic Warming Overtakes 2,000 Years of Natural Cooling" (http:/ / www2. ucar. edu/ news/ 846/arctic-warming-overtakes-2000-years-natural-cooling). UCAR. September 3, 2009. . Retrieved 19 May 2011.Bello, David (September 4, 2009). "Global Warming Reverses Long-Term Arctic Cooling" (http:/ / www. scientificamerican. com/ article.cfm?id=global-warming-reverses-arctic-cooling). Scientific American. . Retrieved 19 May 2011.

[8] Richard A Muller, Gordon J. F. MacDonald (1997). "Glacial Cycles and Astronomical Forcing". Science 277 (5323): 215–8.Bibcode 1997Sci...277..215M. doi:10.1126/science.277.5323.215.

[9] "Origin of the 100 kyr Glacial Cycle: eccentricity or orbital inclination?" (http:/ / muller. lbl. gov/ papers/ nature. html). Richard A Muller. .Retrieved March 2, 2005.

[10] Milankovitch, Milutin (1998) [1941]. Canon of Insolation and the Ice Age Problem. Belgrade: Zavod za Udz̆benike i Nastavna Sredstva.ISBN 86-17-06619-9.; see also "Astronomical Theory of Climate Change" (http:/ / www. ncdc. noaa. gov/ paleo/ milankovitch. html). .

[11] Wunsch, Carl (2004). "Quantitative estimate of the Milankovitch-forced contribution to observed Quaternary climate change". QuaternaryScience Reviews 23 (9–10): 1001–12. Bibcode 2004QSRv...23.1001W. doi:10.1016/j.quascirev.2004.02.014.

[12] Rial, J.A. (October 2003), "Earth’s orbital eccentricity and the rhythm of the Pleistocene ice ages: the concealed pacemaker" (http:/ / web.archive. org/ web/ 20110720092801/ http:/ / www. geolab. unc. edu/ faculty/ rial/ GPCRial2. pdf), Global and Planetary Change, archivedfrom the original (http:/ / www. geolab. unc. edu/ faculty/ rial/ GPCRial2. pdf) on 2011-07-20,

[13] Ghil, Michael (1994). "Cryothermodynamics: the chaotic dynamics of paleoclimate". Physica D 77 (1–3): 130–159.Bibcode 1994PhyD...77..130G. doi:10.1016/0167-2789(94)90131-7.

[14] Gildor H, Tziperman E (2000). "Sea ice as the glacial cycles' climate switch: Role of seasonal and orbital forcing". Paleoceanography 15(6): 605–615. Bibcode 2000PalOc..15..605G. doi:10.1029/1999PA000461.

[15] Zachos JC, Shackleton NJ, Revenaugh JS, Pälike H, Flower BP (April 2001). "Climate response to orbital forcing across theOligocene-Miocene boundary" (http:/ / www. scencemag. org/ cgi/ pmidlookup?view=long& pmid=11303100). Science 292 (5515): 27–48.Bibcode 2001Sci...292..274Z. doi:10.1126/science.1058288. PMID 11303100. .

[16][16] Imbrie and Imbrie; Ice Ages, solving the mystery, p 158[17] F. Varadi, B. Runnegar, M. Ghil (2003). "Successive Refinements in Long-Term Integrations of Planetary Orbits" (http:/ / astrobiology.

ucla. edu/ OTHER/ SSO/ SolarSysInt. pdf) (PDF). The Astrophysical Journal 592: 620–630. Bibcode 2003ApJ...592..620V.doi:10.1086/375560. .

[18] http:/ / www. ncdc. noaa. gov/ paleo/ milankovitch. html[19] J Imbrie, J Z Imbrie (1980). "Modeling the Climatic Response to Orbital Variations". Science 207 (4434): 943–953.

Bibcode 1980Sci...207..943I. doi:10.1126/science.207.4434.943. PMID 17830447.[20] Berger A, Loutre MF (2002). "Climate: An exceptionally long interglacial ahead?". Science 297 (5585): 1287–8.

doi:10.1126/science.1076120. PMID 12193773.[21] http:/ / www. ifa. hawaii. edu/ ~norb1/ Papers/ 2008-milank. pdf[22] http:/ / adsabs. harvard. edu/ abs/ 2008GeoRL. . 3518201S[23] http:/ / ams. confex. com/ ams/ 90annual/ techprogram/ paper_165827. htm[24] http:/ / www. youtube. com/ watch?v=e9sfNegkpPE[25] http:/ / www. universetoday. com/ 46308/ lake-asymmetry-on-titan-explained/[26] http:/ / www. livescience. com/ 1349-sun-blamed-warming-earth-worlds. html[27] http:/ / mmcirvin. livejournal. com/ 383255. html[28] http:/ / altbib. com/ t/ Triton/ framed/ 1

Milankovitch cycles 10

Further reading• Roe G (2006). "In defense of Milankovitch". Geophysical Research Letters 33 (24): L24703.

Bibcode 2006GeoRL..3324703R. doi:10.1029/2006GL027817. This shows that Milankovitch theory fits the dataextremely well, over the past million years, provided that we consider derivatives.

• Edvardsson S, Karlsson KG, Engholm M (2002). "Accurate spin axes and solar system dynamics: Climaticvariations for the Earth and Mars". Astronomy and Astrophysics 384 (2): 689. Bibcode 2002A&A...384..689E.doi:10.1051/0004-6361:20020029. This is the first work that investigated the derivative of the ice volume inrelation to insolation (page 698).

• Zachos J, Pagani M, Sloan L, Thomas E, Billups K (2001). "Trends, Rhythms, and Aberrations in Global Climate65 Ma to Present". Science 292 (5517): 686–693. Bibcode 2001Sci...292..686Z. doi:10.1126/science.1059412.PMID 11326091.This review article discusses cycles and great-scale changes in the global climate during the Cenozoic Era.

External links• Ice Age – Milankovitch Cycles – National Geographic Channel (http:/ / channel. nationalgeographic. com/

channel/ videos/ ice-age-cycles/ )• The Coming Ice Age – Robert Felix – Red Ice Radio (http:/ / www. youtube. com/ watch?v=Sx7dcoe_Mck)• Milankovitch Cycles and Glaciation (http:/ / www. homepage. montana. edu/ ~geol445/ hyperglac/ time1/

milankov. htm)• The Milankovitch band (http:/ / web. archive. org/ web/ 20080729060933/ http:/ / www. agu. org/ revgeophys/

overpe00/ node6. html), Internet Archive of American Geophysical Union lecture• Some history of the adoption of the Milankovitch hypothesis (and an alternative) (http:/ / muller. lbl. gov/ pages/

IceAgeBook/ IceAgeTheories. html)• More detail on orbital obliquity also matching climate patterns (http:/ / muller. lbl. gov/ papers/ sciencespectra.

htm)• "Milutin Milankovitch" (http:/ / earthobservatory. nasa. gov/ Features/ Milankovitch/ milankovitch. php). On the

Shoulders of Giants. Retrieved January 15, 2010.• Potential Problems with Milankovitch Theory (http:/ / www. detectingdesign. com/ milankovitch. html) by Sean

Pitman (http:/ / www. detectingdesign. com)• The Seasons (http:/ / aa. usno. navy. mil/ faq/ docs/ seasons_orbit. php)• The NOAA page on Climate Forcing Data (http:/ / www. ncdc. noaa. gov/ paleo/ forcing. html) includes

(calculated) data on orbital variations over the last 50 million years and for the coming 20 million years.• The orbital simulations by Varadi, Ghil and Runnegar (2003) (http:/ / astrobiology. ucla. edu/ OTHER/ SSO/ )

provide another, slightly different series for orbital eccentricity, and also a series for orbital inclination• ABC: Earth wobbles linked to extinctions (http:/ / www. abc. net. au/ science/ news/ stories/ 2006/ 1763328. htm)

Article Sources and Contributors 11

Article Sources and ContributorsMilankovitch cycles  Source: http://en.wikipedia.org/w/index.php?oldid=536538201  Contributors: 069952497a, AVM, Abmcdonald, Ahoerstemeier, Akradecki, Alexander.stohr, Alexjohnc3,Arthur Rubin, AstroWiki, Atosecond, AussieBoy, Awickert, Bender235, Bj norge, Bobblehead, BozMo, Bruce Hall, Btyner, Bubba73, CMG, Can't sleep, clown will eat me, Canjth, Catdog181,Cdrigby, Cesiumfrog, Charles Matthews, Ckatz, Climateguru, Colonies Chris, ConfuciusOrnis, CopperKettle, Cp111, Crzysdrs, Curps, DHeyward, Darkolaird, Dave souza, David Moe, DerGolem, Dragons flight, Duncan.Hull, Dysmorodrepanis, Editor993, Emijrp, Eric Shalov, Etacar11, Eve Hall, Everyking, Ewlyahoocom, Eyreland, Fama Clamosa, Farseer, FlagrantUsername,FraKa, Fred Bradstadt, Friendly Neighbour, Gaianauta, Gbirley, Geek12597, Gene s, Geraldshields11, Glenn, GregBenson, HJJHolm, Hallucegenia, Heron, Hgilbert, IanAnonymous,IanOfNorwich, Incredio, JEBrown87544, JForget, Jackfork, Jaganath, Jalwikip, Jbergquist, JimR, Joe Kress, John Abbe, John Palkovic, John Quiggin, John Riemann Soong, Jorfer, JorisvS,Joseph Solis in Australia, Jujutacular, Julesd, Jyril, Karajade, KimDabelsteinPetersen, LCE1506, Lambiam, Lamro, LedgendGamer, Literacola, Lumidek, Lvzon, Marek69, Markls8,Massimiliano Lincetto, Matt Borak, Meanos, Memetics, Mhdarin, Michael Hardy, Michaelbarreto, Michur, MigueldelosSantos, Mikenorton, Mozzerati, Myleslong, Mysid, Mårten Berglund,Natanaelr, Nathan Johnson, Nikmix, Novangelis, Nrcprm2026, Obradovic Goran, Octopus-Hands, Ohms law, Orbitalforam, Pauli133, Pfvlloyd, Pgossens, Plrk, Prester John, Pro crast in a tor,Purdygb, Q Science, Quaoar, Quidproquo2004, RDBrown, RG2, Random account 47, RayTomes, Rich Farmbrough, RingtailedFox, Rjwilmsi, RobertM525, RockMagnetist, Rorro, Rrburke,Rtdrury, Ruud Koot, Rāmā, SAE1962, SEWilco, Sae1962, Safalra, Saintonge235, SalvNaut, Saperaud, Scott Illini, ServiceAT, Shanes, ShoWPiece, Skylark42, Smilesfozwood, Smith609,Sophie, Steve98052, SteveOak, Stuvan, SunSw0rd, Susan1000, Tamfang, Tcwilliams, Terjepetersen, Tfr000, Thaimoss, That Guy, From That Show!, The Thing That Should Not Be, The way,the truth, and the light, Thesevenseas, Thorwald, Topsydog, Trioculite, Try0yrt, Twang, Ugajin, Unholy.Asmodeus, Velvetron, Vinay Jha, Vsmith, Vuong Ngan Ha, WVhybrid, Wavelength,Wik, William M. Connolley, Wilson44691, Woohookitty, Worldrimroamer, Yamara, Yoshirocks8, Zandperl, Zarateman, Zbayz, Свифт, 248 anonymous edits

Image Sources, Licenses and ContributorsImage:MilankovitchCyclesOrbitandCores.png  Source: http://en.wikipedia.org/w/index.php?title=File:MilankovitchCyclesOrbitandCores.png  License: Creative Commons Attribution 3.0 Contributors: IncredioImage:Eccentricity zero.svg  Source: http://en.wikipedia.org/w/index.php?title=File:Eccentricity_zero.svg  License: Public Domain  Contributors: NASA, MysidImage:Eccentricity half.svg  Source: http://en.wikipedia.org/w/index.php?title=File:Eccentricity_half.svg  License: Public Domain  Contributors: NASA, MysidImage:Earth obliquity range.svg  Source: http://en.wikipedia.org/w/index.php?title=File:Earth_obliquity_range.svg  License: Public Domain  Contributors: NASA, MysidImage:Earth precession.svg  Source: http://en.wikipedia.org/w/index.php?title=File:Earth_precession.svg  License: Public Domain  Contributors: NASA, MysidImage:Precessing Kepler orbit 280frames e0.6 smaller.gif  Source: http://en.wikipedia.org/w/index.php?title=File:Precessing_Kepler_orbit_280frames_e0.6_smaller.gif  License: CreativeCommons Attribution 3.0  Contributors: WillowWImage:precession and seasons.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Precession_and_seasons.jpg  License: GNU Free Documentation License  Contributors:User:GregBensonImage:Cyclic deposits.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Cyclic_deposits.jpg  License: Creative Commons Attribution 3.0  Contributors: VerisimilusImage:Vostok 420ky 4curves insolation.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Vostok_420ky_4curves_insolation.jpg  License: Public Domain  Contributors:Alexander.stohr, Bender235, Elvey, Koavf, Mikhail Ryazanov, Pieter Kuiper, Pmsyyz, Suarez ruibal, Telim tor, TommyBee, 3 anonymous editsImage:Five Myr Climate Change.svg  Source: http://en.wikipedia.org/w/index.php?title=File:Five_Myr_Climate_Change.svg  License: unknown  Contributors: Dragons flight, svg by JoImage:InsolationSummerSolstice65N.png  Source: http://en.wikipedia.org/w/index.php?title=File:InsolationSummerSolstice65N.png  License: Public Domain  Contributors: Incredio

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